Zcash Network Upgrade to Freeze $16 Million in Old Privacy Pool

Zcash users face deadline to move funds

Zcash users have less than a day to move approximately $16 million from the network's oldest privacy pool before an upgrade makes the funds unspendable. Zcash is a privacy network that allows users to hide transaction details. The upcoming NU7 upgrade will disable the ability to spend coins held in the Sprout pool, even for owners who still have their private keys.

As of Thursday morning, about 12,226 ZEC remained in the Sprout pool. This is a significant decrease from the 22,263 ZEC held there one week ago. Most of these funds were moved on Sunday, with only a small amount transferred out on Wednesday.

Key details of the Sprout pool retirement

• About 12,226 ZEC remains in the Sprout pool, valued at roughly $16 million.
• The upgrade is scheduled for block 3,543,405, expected around 9:30 p.m. ET on Thursday.
• Users with addresses starting with "zc" are affected by this change.
• The NU7 upgrade will also reduce block times from 75 seconds to 25 seconds.

Official specifications for the NU7 upgrade

According to the ZIP 2003 specification, the NU7 upgrade will reject "version-4" transactions. This specific transaction format is the only way to spend coins currently held in the Sprout pool. Once the upgrade is active, any balance remaining in the pool will become unspendable under the new network rules.

Confirmed details regarding the fund freeze

The Sprout pool was the original privacy pool launched with Zcash in 2016. It has since been replaced by newer technology. While the public pool balance shows how many coins remain, it does not identify the owners. It is also unknown how many of these coins belong to wallets where the private keys have been lost. The coins will technically remain part of the total Zcash supply but will be locked.

Uncertainty over future fund recovery

The official specifications for the upgrade leave open the possibility of restoring access to these funds through a future network update. However, the documentation also warns that the ability to spend these coins may never be re-enabled. There is currently no confirmed timeline or guarantee for such a restoration.

Why the network is retiring the Sprout pool

The decision to retire the Sprout pool is intended to reduce software complexity and security risks. Maintaining the older transaction machinery required for Sprout adds a burden to the software that checks Zcash payments. By removing this complexity, developers aim to improve the overall security and efficiency of the network.

The timeline for the network upgrade

The upgrade is tied to a specific block number on the blockchain, which is a digital ledger that records transactions. At the current rate of block production, the upgrade is estimated to occur on Thursday evening. However, the exact time depends on how quickly miners find blocks, which could push the activation into early Friday morning.

Sources

• CoinDesk
• ZecStats
• Zcash Improvement Proposals (ZIPs)